Naval History Magazine, Dec. 2012
From the 1920s into World War II several nations developed high-performance floatplane aircraft. Indeed, some were among the fastest aircraft of their time. During World War II, the British evaluated float configurations with several versions of the famed Supermarine Spitfire fighter, and the U.S. Navy fitted a single Grumman F4F-3 Wildcat with floats. But only Japan pursued large-scale operational floatplane fighters during the war, primarily with the Nakajima A6M2-N Rufe, a variant of the Mitsubishi A6M Zero, or Zeke.
After the war the British developed a flying-boat fighter, the turbojet-powered Saunders-Roe SR.A/1.Â 1Â And the U.S. Navy undertook development of a supersonic â€śwater-basedâ€ť fighter, the Convair F2Y Seadart.Â 2
Convair had previously produced several successful seaplanes, most notably the PBY Catalina flying boat. That aircraftâ€”produced in larger numbers than any other seaplane by any countryâ€”was flown in every theater of World War II by the United States and several other nations. But the company had limited turbojet and fighter experience. However, Convairâ€™s Hydrodynamic Laboratory was exploring several subsonic seaplane concepts, some given the project name Skate. At the time, the U.S. Navy was considering advanced seaplanes for a number of rolesâ€”cargo, strike, minelaying, reconnaissance, patrol, and fighter. Fitting a fighter with floatsâ€”or using the British flying-boat configurationâ€”would introduce considerable drag on the aircraft. Convair engineers conceived a plan to employ retractable hydro-skis for waterborne operations.
The Navy awarded Convair a contract for two XF2Y-1 prototype aircraft in January 1951. The first test flight occurred on 9 April 1953, in San Diego Bay, with the companyâ€™s E. D. â€śSamâ€ť Shannon at the controls.
According to a contemporary Navy publication, â€śThe intense interest [in the aircraft] is understandable, for this was an airplane which wrapped up in one package more new and untried features than any aeronautical design in many a day.â€ť3Â The delta-winged, tailless aircraftâ€™s fuselage provided flotation at rest and low speeds. As the aircraft accelerated for takeoff, the fuselage, except for a small part of the tail, was lifted clear of the water by twin, fully retractable hydro-skis. This scheme brought the delta wing to the proper attitude for takeoff. The hydro-skis were planing skis, obtaining lift in the same manner as a person using water skis. Operations in waves up to five feet high were considered feasible.
No horizontal tail surfaces or flaps were provided. Control was by elevons and rudder. A rudder was provided for maneuvering at low speeds on the water. It was also employed in flight as a speed brake, being linked to the elevons to automatically coordinate banked turns.
The first aircraftâ€”the XF2Y-1â€”was fitted with twin Westinghouse J34 turbojet non-afterburning engines in the upper fuselage that could develop 3,400 pounds static thrust each. Later aircraft would have twin Westinghouse XJ46-WE-2 turbojet engines with afterburners provided. Takeoff after a 30-second warm-up was estimated to be 15 seconds at military power plus afterburnerâ€”a total of more than 12,000 pounds static thrust. The definitive F2Y-2 was to have an empty weight of 12,652 pounds and a maximum takeoff weight of 16,527 pounds.
The relatively successful early trials of the Seadart prototypes led to tests with a dock landing ship (LSD) being employed to evaluate possible open-sea support of the aircraft. This was similar to the concept considered for the Navyâ€™s Martin P6M Seamaster, a flying-boat strike/minelaying/reconnaissance aircraft.Â 4
Following the flight of the XF2Y-1, the Navy planned an initial production run of 17 aircraft to further evaluate the feasibility of a sea-based interceptor. However, the order that was placed was for an additional three prototypes, a total of five aircraft, with the latter four being designated YF2Y-1. The second aircraft was lost during a low-level flight at about 575 mph over San Diego Bay on 4 November 1954. Test pilot Charles E. â€śChuckâ€ť Richbourg was killed in the crash.
Earlier in 1954, the XF2Y-1 was refitted with a single hydro-ski that was not fully retractable. Taxi tests of the new configuration began in the fall and the aircraft was found to lack hydrodynamic stability and control. Later tests of rigid non-retractable skis were conducted, with one of the skis having a hydrofoil shape. More than 100 ski configurations were considered for the aircraft.
The third aircraftâ€”the second YF2Y-1â€”began flight tests on 4 March 1955. This aircraft had small wheels at the rear of its twin skis plus a small swivel-tail wheel to provide tail-down mobility when on a seaplane ramp or tarmac.
High-performance flight tests were canceled after the loss of the No. 2 Seadart, but taxi and flight trials continued. Four 1,000-pound-thrust rocket boosters were evaluated but were not successful, causing severe vibration and pounding loads on the aircraft and pilot. Additional modifications were made to the airplane, but in time it became clear that the hydro-ski configuration was not feasible for a high-performance operational aircraft.
Flight trials of various Seadart configurations continued until 1956, when the project was halted. Only three aircraft flew; engines were never installed in the last two YF2Y-1s. (The two surviving flight-test aircraft and two non-flying aircraft still exist in museums.) In a strange postscript to the Seadart story, in 1962â€”some six years after the projectâ€™s termination and the planeâ€™s last flightâ€”the YF2Y-1 Seadart was assigned the then-new tri-service unified aircraft designation of YF-7A.
The concept of a supersonic seaplane fighterâ€”the F2Y Seadartâ€”was another of the fascinating and envelope-pushing aircraft developed in the early jet age. And, like so many others of its time, it was not to be.
1. The subsonic SR.A/1 first flew on 16 July 1947, with three prototypes being produced and test flights continuing until 1951. No production was undertaken.
2. See B. J. Long,Â Convair XF2Y-1 and YF2Y-1 SeaDartÂ (Simi Valley, CA: Steve Ginter, 1992) and B. J. Long, â€śSeadart: U.S. Navy XF2Y-1 and YF2Y-1 Experimental Supersonic Seaplanes,â€ťÂ American Aviation Historical Society JournalÂ (1st Quarter 1979), 2â€“12. Long was Convairâ€™s project engineering test pilot for the aircraft.
3. â€śSeadart . . . â€ťÂ Naval Aviation Confidential BulletinÂ (August 1953), 2.
4. See N. Polmar, â€śThe Last Flying Boat,â€ťÂ Naval HistoryÂ (August 1999), 53.